The present invention relates to a hydraulic control system for an automatic transmission.
It is a well known technique to provide an accumulator in a hydraulic control system for an automatic transmission so as to alleviate a shock which takes place inherently during shift by gradually increasing a fluid pressure supplied to fluid operated friction units. In the case of a conventional automatic transmission, for example, a four speed automatic transmission, in order to alleviate a shock taking place during a downshift from the four speed ratio to the third speed ratio, the second speed ratio or the first speed ratio (i.e., 4--3 downshift, 4--2 downshift, 4--1 downshift) and a shock taking place when a manual valve is moved from a "N" position thereof to a "D" position thereof, a plurality of accumulators are required, each being adapted to operate during one of these shifts. However, providing the plurality of accumulators creates a problem that a hydraulic circuit becomes complicated and a large space is required for the installation of the accumulators.